April showers truly bring May flowers. May is often the peak bloom time for spring-blooming plants in Iowa. While crabapple and lilac flowers often garner considerable attention in May, there are several perennials that produce an equally impressive display of spring blooms.
Sunny sites encourage abundant blooms. Species like iris, false indigo, blue star, ornamental onion, and peony are noted for their bountiful blooms in May.
Bearded iris (Iris hybrids) is noted for large colorful flowers on plants approximately 2 to 3 feet tall. Flowers are available in all colors of the rainbow. Bearded iris may be the most recognizable iris available, but it is not the only species of iris that blooms in spring. Crested iris (Iris cristata) is a dwarf iris that blooms before bearded iris. Siberian iris (Iris sibirica) and Japanese iris (Iris ensata) bloom a couple of weeks after bearded iris. These iris species do not have the variety of flower colors as bearded iris, but they greatly extend the bloom time in the landscape.
False indigo (Baptisia australis) produces spires of blue or lavender flowers on 3-foot-tall plants. The pea-like flowers develop into showy black seed pods later in summer. This species and several others are native throughout the Midwest. Several hybrids of false indigo have showy deeper purple, white, or yellow flowers.
Blue star (Amsonia tabernaemontana) has light blue, star-shaped flowers on top of 3- to 4-foot- tall perennials. Blue star is also noted for its attractive golden-yellow foliage color in fall. Thread leaf bluestar (Amsonia hubrichtii) has finer foliage with equally impressive floral displays. Both species are native to the central US.
Peony flowers often close out the month of May with a bounty of blooms. The showy pink, white, lavender, or burgundy-red flowers top 2-3-foot tall plants around Memorial Day. While Oriental peonies (Paeonia hybrids) are the quintessential spring-blooming peony, gardeners also treasure fern leaf peonies (Paeonia tenuifolia). Fern leaf peonies are highly prized heirlooms that produce dark red blooms on fine-textured foliage earlier in May. Tree peonies (Paeonia suffruticosa) and hybrid ITOH peonies also produce exquisite spring blooms.
Other Sun-Loving Perennials
Other sun-loving perennials that bloom in May include poppies, dianthus, yarrow, perennial geranium, delphinium, foxglove, penstemon, and catmint.
Shade-loving perennials tend to perform better in part to full shade. Sometimes the blooms last longer in the shade as these sites are often a bit cooler. These species start after most of the woodland wildflowers pass. Perennials like bleeding heart, columbine, and Jacob’s ladder are noted for their bright blooms in May.
Old-fashioned bleeding heart (Lamprocapnos spectabilis) has distinctive pink and white or red and white flowers on arching stems in early to mid-May. Plants are often 2 to 3 feet tall and wide. They perform best in part shade that receives a couple hours of direct sun. This species is ephemeral like many woodland wildflowers, meaning that plants go dormant in mid to late summer when it gets hot.
Columbine flowers produce delicate nodding flowers in a wide range of colors. There are almost as many columbine colors as bearded iris flower colors. Iowa’s native columbine (Aquilegia canadensis) has cardinal and gold flowers and prefers woodland sites with well-drained soils. Several other species of columbine are native to various regions in the US. Hybrids are noted for their showy and abundant red, yellow, white, blue, pink, lavender, or bicolor flowers. While columbine tends to be short-lived in the landscape, it frequently reseeds so new seedlings replace older ones.
Jacob’s ladder (Polemonium reptans) is another spring bloomer that is native to the central US. The light blue flowers shine atop 1 to 2 feet tall plants. Several cultivars of the Jacob’s ladder that is native to Europe (Polemonium caeruleum) have variegated foliage that remain showy in shady gardens throughout the summer.
Several groundcovers also bloom well in spring in shady sites. Lily of the valley (Convallaria majalis) is noted for its white, bell-shaped, fragrant flowers in May. Vinca (Vinca minor) produces blue/purple or white flowers. Spotted deadnettle (Lamium maculatum) often has abundant white, pink, or lavender flowers on green and silver variegated leaves. And barrenwort (Epimedium species and hybrids) has delicate yellow, pink, orange, lavender, or white flowers above the arrowhead-like foliage in spring. And several cultivars of bugleweed (Ajuga reptans) produce purple, blue, or white flower spikes above dark green, burgundy, or variegated foliage.
Learn more about groundcovers for shady locations in this article: Groundcovers for Shade
Other Shade-Loving Perennials
Other shade-loving perennials that bloom in May include: Jack-in-the-pulpit, trillium, Solomon’s seal, foamflower, and coral bells.
Celebrate spring in your landscape by planting and enjoying a bounty of blooms in the month of May!